ActionScript for Flash MX: The Definitive Guide, Second Edition

This is the Title of the Book, eMatter Edition

Copyright © 2007 O’Reilly & Associates, Inc. All rights reserved.

Datatype Conversion

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examine the cases in which automatic conversions will occur and the results of con-

verting a datum from one type to another.

Datatype Conversion

Take a closer look at the example from the previous section. In that example, each

datum—“1” and 2—belonged to its own datatype; the first was a string and the sec-

ond was a number. We saw that the interpreter joined the two values together to

form the string “12”. Note that the interpreter first had to convert the number 2 into

the string “2”. Only after that automatic conversion was performed could the value

“2” be joined (concatenated) to the string “1”.

Datatype conversion simply means changing the type of a datum. Not all datatype

conversions are automatic; we may also change a datum’s type explicitly in order to

override the default datatype conversion that ActionScript would otherwise perform.

Explicit conversion is known as typecasting, or simply casting.

Automatic Type Conversion

Whenever we use a value in a context that does not match the expected datatype, the

interpreter attempts a conversion. That is, if the interpreter expects data of type A,

and we provide data of type B, the interpreter will attempt to convert our type B data

into type A data. For example, in the following code we use the string “Flash” ...